[SOLVED] Help needed with Gallag (Galaga bootleg) text and sprite weird glitch [Video added]

[tiburciod]

Hi forums,

I'm pulling my hair off with a Gallag (Galaga bootleg); Im dealing with glitches that might be one or multiple ICs. This is what is going on:

Text and sprites in the upright mode look garbled, but when the game rotate (or sprites rotate when dives) , it looks ok. It Looks like that is flipping partially and some pixel lines are stuck. I have been looking at the LS161s and LS86s, but without the schematics, it is challenging to understand the pipeline. The starfield seems perfect.

Here is a video of what's going on. Notice also the glitch in the pattern at the start. I'm flipping the screen by grounding the flip pin on an LS86.

 

[tiburciod]

Well, it was another Fushitsu LS74 at location B8. That 74 gets the clock from the 1st flip-flop from the output of the 2nd FLIP-FLOP, and that one was always high. This Gallag board without the schematics is a nightmare since it has many inputs just floating and not connected on several chips. I ended up shorting pins here and there to understand the areas and finally found that 74.